Circuit breaker attachments are being used ever more widely to expand and supplement the functionality of circuit breakers. Circuit breaker locking devices are one example of circuit breaker attachments. When a circuit on the load side of a circuit breaker requires maintenance or is not permitted to pass a current, a circuit breaker locking device can be used to lock the circuit breaker in the OFF position, in order to prevent other people from mistakenly closing the circuit breaker, and thereby ensure the safety or maintenance personnel or the reliable operation of electrical equipment. However, existing circuit breaker locking devices have quite complex structures, and must be installed and secured in place with a high degree of precision, making installation inconvenient.